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authorMike Rapoport <rppt@linux.vnet.ibm.com>2017-02-24 14:58:28 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-24 17:46:55 -0800
commit27d02568f529e908399514dfbee8ee43bdfd5299 (patch)
treec8ff36cdc63f9a500355cdec086205de21033fda /mm
parentca49ca7114553587736fe78319e22f073b631380 (diff)
downloadlinux-27d02568f529e908399514dfbee8ee43bdfd5299.tar.gz
userfaultfd: mcopy_atomic: return -ENOENT when no compatible VMA found
The memory mapping of a process may change between #PF event and the call to mcopy_atomic that comes to resolve the page fault. In such case, there will be no VMA covering the range passed to mcopy_atomic or the VMA will not have userfaultfd context. To allow uffd monitor to distinguish those case from other errors, let's return -ENOENT instead of -EINVAL. Note, that despite availability of UFFD_EVENT_UNMAP there still might be race between the processing of UFFD_EVENT_UNMAP and outstanding mcopy_atomic in case of non-cooperative uffd usage. [rppt@linux.vnet.ibm.com: update cases returning -ENOENT] Link: http://lkml.kernel.org/r/20170207150249.GA6709@rapoport-lnx [aarcange@redhat.com: merge fix] [akpm@linux-foundation.org: fix the merge fix] Link: http://lkml.kernel.org/r/1485542673-24387-5-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Pavel Emelyanov <xemul@virtuozzo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/userfaultfd.c58
1 files changed, 28 insertions, 30 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 1e5c2f9..9f0ad2a 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -197,22 +197,25 @@ retry:
* retry, dst_vma will be set to NULL and we must lookup again.
*/
if (!dst_vma) {
- err = -EINVAL;
+ err = -ENOENT;
dst_vma = find_vma(dst_mm, dst_start);
if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
goto out_unlock;
-
- if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
- goto out_unlock;
-
/*
- * Make sure the remaining dst range is both valid and
- * fully within a single existing vma.
+ * Only allow __mcopy_atomic_hugetlb on userfaultfd
+ * registered ranges.
*/
+ if (!dst_vma->vm_userfaultfd_ctx.ctx)
+ goto out_unlock;
+
if (dst_start < dst_vma->vm_start ||
dst_start + len > dst_vma->vm_end)
goto out_unlock;
+ err = -EINVAL;
+ if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
+ goto out_unlock;
+
vm_shared = dst_vma->vm_flags & VM_SHARED;
}
@@ -221,12 +224,6 @@ retry:
goto out_unlock;
/*
- * Only allow __mcopy_atomic_hugetlb on userfaultfd registered ranges.
- */
- if (!dst_vma->vm_userfaultfd_ctx.ctx)
- goto out_unlock;
-
- /*
* If not shared, ensure the dst_vma has a anon_vma.
*/
err = -ENOMEM;
@@ -404,22 +401,35 @@ retry:
* Make sure the vma is not shared, that the dst range is
* both valid and fully within a single existing vma.
*/
- err = -EINVAL;
+ err = -ENOENT;
dst_vma = find_vma(dst_mm, dst_start);
if (!dst_vma)
goto out_unlock;
/*
- * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
- * it will overwrite vm_ops, so vma_is_anonymous must return false.
+ * Be strict and only allow __mcopy_atomic on userfaultfd
+ * registered ranges to prevent userland errors going
+ * unnoticed. As far as the VM consistency is concerned, it
+ * would be perfectly safe to remove this check, but there's
+ * no useful usage for __mcopy_atomic ouside of userfaultfd
+ * registered ranges. This is after all why these are ioctls
+ * belonging to the userfaultfd and not syscalls.
*/
- if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
- dst_vma->vm_flags & VM_SHARED))
+ if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;
if (dst_start < dst_vma->vm_start ||
dst_start + len > dst_vma->vm_end)
goto out_unlock;
+ err = -EINVAL;
+ /*
+ * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
+ * it will overwrite vm_ops, so vma_is_anonymous must return false.
+ */
+ if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
+ dst_vma->vm_flags & VM_SHARED))
+ goto out_unlock;
+
/*
* If this is a HUGETLB vma, pass off to appropriate routine
*/
@@ -427,18 +437,6 @@ retry:
return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
src_start, len, zeropage);
- /*
- * Be strict and only allow __mcopy_atomic on userfaultfd
- * registered ranges to prevent userland errors going
- * unnoticed. As far as the VM consistency is concerned, it
- * would be perfectly safe to remove this check, but there's
- * no useful usage for __mcopy_atomic ouside of userfaultfd
- * registered ranges. This is after all why these are ioctls
- * belonging to the userfaultfd and not syscalls.
- */
- if (!dst_vma->vm_userfaultfd_ctx.ctx)
- goto out_unlock;
-
if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
goto out_unlock;